The present invention relates to a method for preparing a printed product by transferring a transfer layer of an intermediate transfer recording medium on which an image is formed, via a transferring adhesive layer, on a surface of a transfer-receiving material with an excellent adhesive property.
There is known a method of preparing a printed product using an intermediate transfer recording medium. The intermediate transfer recording medium is hitherto used to form a printed product which is formed so that an image is recorded on a receptor layer then the receptor layer is transferred onto a transfer-receiving material. On the receptor layer, images are recorded by thermal transfer recording methods using a thermal transfer sheet, depending on a composition of materials, forming high quality images. Further, because a receptor layer may have an excellent adhesive property with a transfer-receiving material, or can be transferred to a transfer-receiving material via an adhesive layer with an adequate adhesive property, this method is preferably used for a transfer-receiving material on which high quality images cannot be formed directly because coloring materials hardly migrate to the transfer-receiving material, and which easily fuse and adhere to a coloring material layer during thermal transferring.
FIG. 12 shows a schematic sectional view of one example of a typical intermediate transfer recording medium. An intermediate transfer recording medium 101 is composed of a base film 102 and a transfer layer 112 which comprises at least a receptor layer 105. On the receptor layer 105, images 106 are formed through thermal transferring with a thermal-transferring sheet having a coloring material layer. The transfer layer 112, having the receptor layer 105 on which images 106 are formed, is separated from a base film 102, and transferred on the transfer-receiving material, then images 106 as an objective are formed on the transfer-receiving material.
By using such an intermediate transfer recording medium, high resolution and high quality images can be transferred and formed on a transfer-receiving material. Because the required images, for example or a letter a photograph of one's face is formed on the transfer layer of the intermediate transfer recording medium in advance, the images can then be formed on the transfer-receiving material by transferring. The method is superior to the methods because the images can be easily formed on transfer-receiving material even if the images exist individually, such as a booklet of a passport and a base material of a card. Further, additional images can be formed through an image, for example a signature can be entered or printed on a transfer-receiving material in advance, then a transfer layer formed images such as letters and pictures can be transferred from the intermediate transfer recording medium. Therefore, the intermediate transfer recording medium can be preferably used to form an identification document such as a passport, and a printed product such as a credit card, an ID card, and so on.
In this thermal transfer method, a thermal transfer sheet, composed of a coloring material layer formed on a base film, and a transfer-receiving material on which a receptor layer is formed as occasion demands, are pressure-welded between a heating device such as thermal head and a platen roll, and heating portions of the heating device are selectively heated in accordance with the images to be transferred, so that a coloring material contained in the coloring material layer on the thermal transfer sheet is transferred on the transfer-receiving material thereby to record the images thereon. These thermal transfer methods are generally classified into a fusion thermal transfer method and a sublimation transfer method.
The fusion thermal transfer method is a method in which a thermal transfer sheet carrying a heat fusible ink layer is heated by the heating means of the type mentioned above and a softened heat fusible ink is transferred on a transfer-receiving material such as natural fiber paper or plastic sheet thereby to form an image on the transfer-receiving material. The heat fusible ink layer used in this method will be prepared by dispersing a coloring material such as pigment into a binder such as heat fusible wax or resin, and the heat fusible ink layer is carried by a base film such as plastic film. An image formed by this fusion thermal transfer method has an improved high density and sharpness, and hence, this method is more applicable to the recording of binary images such as letters or lines. Colored or multiple-colored images can be formed by using a thermal transfer sheet provided with heat fusible ink layers of yellow, magenta, cyan, black and the like and recording them on the transfer-receiving material.
On the other hand, the sublimation thermal transfer method is a method in which a thermal transfer sheet carrying a sublimation dye layer is heated by the heating means of the type mentioned above so as to sublimate the sublimation dye contained in the dye layer, and the dye is then transferred on a receptor layer formed on the transfer-receiving material, thus forming an image. The sublimation dye layer used in this method will be prepared by dissolving or dispersing the sublimation dye as coloring material into a binder such as resin, and the sublimation dye layer is carried by a base film such as plastic film. According to such sublimation thermal transfer method, since transferring amount of the dye can be controlled in dot unit in accordance with energy amount of the heating device such as thermal head, a gradation reproduction due to density modulation can be made possible. Furthermore, since the dye material is used as a coloring material, the thus formed image has a transparency, and hence, this method is superior to the reproduction of the intermediate colors at a time when a plurality of dye layers of a plurality of colors are transferred in an overlapped manner. For this reason, a full-colored image with high quality can be formed by transferring the sublimation dye of three or four colors of yellow, magenta and cyan, in addition to black, on the transfer-receiving material in an overlapped manner by using the thermal transfer sheet provided with sublimating dye layers of these three or four colors.
In these image forming methods, it is necessary particularly for the sublimation thermal transfer method that the transfer-receiving material on which an image is to be formed is provided with a dyeing property of the dye. Because of this reason, in a case where the surface of the transfer-receiving material has a less dyeing property, it is almost difficult to form an image on the transfer-receiving material as far as the receptor layer is provided thereon.
For example, the Japanese Patent Laid-open Publication No. SHO 62-264994 discloses a technique for providing a receptor layer on a transfer-receiving material having no dyeing property in a manner that a receptor layer transfer sheet formed by providing the receptor layer on a base film to be separable is preliminarily prepared and this receptor layer is transferred on the transfer-receiving material. According to this technique, a dye is transferred from a dye layer of a thermal transfer sheet to the receptor layer already transferred on the transfer-receiving material to thereby form an image.
Furthermore, in Japanese patent Laid-open Publication No. SHO 62-238791 and the Japanese patent Laid-open Publication No. HEI 4-133793, there is disclosed a technique such that an intermediate transfer recording medium formed by providing the receptor layer on a base film to be separable is preliminarily prepared and an image is formed by transferring a dye from a thermal transfer sheet on this receptor layer. Thereafter, the receptor layer bearing the image is transferred to the transfer-receiving material by heating thus forming the intermediate transfer recording medium. According to these methods, not only on transfer-receiving material with a satisfied dyeing property, but also on transfer-receiving materials with a less dyeing property, and with easily melt-adhering property by heating from thermal head and the like, images can be transferred and formed. An improper influence of uneven surface and formation of a transfer-receiving material can be prevented.
To improve the poor quality of transferring which occurs in the case that adhesive strength between a receptor layer bearing an image and transfer-receiving material is not enough, adhesive strength between the receptor layer and the transfer-receiving material is increased through transferring an adhesive layer on the receptor layer of an intermediate transfer recording medium and/or transfer-receiving material from an adhesive layer transferring sheet, such as disclosed in the Japanese patent Laid-open Publication No. HEI 7-52522.
However, when using the above-mentioned adhesive layer transfer sheet, there are some cases that the problem of adhesive failure cannot be solved because adhesive strength between the receptor layer and the transfer-receiving material is not able to increase. For example, in some cases, an adhesive layer had enough adhesive property with a receptor layer, but not enough with a transfer-receiving material, and there were opposite cases.
The reason why such a case occurs particularly result from recent requirement of a high resolution and a high quality and variety of transfer-receiving material. That is, in order to form an image having a high resolution, the materials of the receptor layer on the outermost surface of the intermediate transfer recording medium are limited, because the receptor layer formed on the outermost surface of the intermediate transfer recording medium must have an excellent dyeing property and be formed by the material which has a excellent thermal separating property with dye transfer sheet. Accordingly, an adhesive layer suitable for a receptor layer to be used, must be selected.
The other side, a demand such that high resolution and high quality images are transferred and formed on the various transfer-receiving materials, is increasing. For example, when required matters for identification such as a picture of one's face and the like print through use of thermal transfer method, usually natural paper is used for a passport, and the quality of the natural paper is different in each country, some of them are worse about smoothness. When images are used for an identification document such as a passport and the like, a receptor layer bearing the image must adhere firmly on the transfer-receiving material, and not be separable easily, thus an adhesive layer suitable for transfer-receiving material must be selected.
Accordingly, there is a problem that an adhesive layer suitable for a receptor layer does not always coincide with an adhesive layer suitable for a transfer-receiving material.
Recently, there is a demand to a printed product, on which the printed product is formed such that a part of a transfer layer of an intermediate transfer recording medium is transferred on the required portion of a transfer-receiving material. For example, there are some cases that a transfer layer on which a picture of one's face is formed to the only designated section of an identification document and a passport. However, conventionally, an adhesive layer is transferred on all surface of a transfer layer of an intermediate transfer recording medium, by means of a roller transfer which is efficient as-a transfer method, then a printed product is obtained through transferring the transfer layer on transfer-receiving material via adhesion layer by means of a roller transfer, again. Accordingly, it is impossible to transfer a part of a transfer layer on a transfer-receiving material with a satisfactory adhesive property.
In case an image is formed on a transfer-receiving material by using an intermediate transfer recording medium, it is carried out by thermal transfer method, which does not depend on via an adhesive layer or not. As a result, there are some possibility that turbulence generate in an image of a printed product because of softening or fluidization of a receptor layer bearing an image.